import logging
import os
from pathlib import Path
import shutil
import subprocess
import re
import sys
from typing import Sequence

_invalid_file_char_regex = re.compile(r'[^a-zA-Z0-9_]')
_variable_regex = re.compile(r'@([A-Z_]+)@')
_logger = logging.getLogger(__name__)
_root: Path

def _exec_checked(args: Sequence[str], **kwargs) -> None:
    subprocess.run(args, stdout=sys.stdout, stderr=sys.stderr, check=True, **kwargs)

def _exec_get_output(args: Sequence[str], **kwargs) -> str:
    return subprocess.run(args, text=True, check=True, capture_output=True).stdout

def _prompt(prefix: str = '> ') -> str:
    sys.stdout.write(prefix)
    sys.stdout.flush()
    return sys.stdin.readline()

def _escape_filename(name: str) -> str:
    return _invalid_file_char_regex.sub('_', name)

def verify_tools() -> None:
    _logger.debug('Verifying all required tools are available...')
    success = True
    if shutil.which('git') is None:
        _logger.error('git not found in PATH')
        success = False
    if shutil.which('scons') is None:
        _logger.error('SCons not found in PATH')
        success = False
    if not success:
        raise RuntimeError('one or more required tools could not be found')

def download_spp() -> None:
    _logger.debug('Checking if Scons++ is checked out...')
    output = _exec_get_output(['git', 'submodule', 'status', 'external/scons-plus-plus'])
    if output[0] in ('+', ' '):
        return
    assert output[0] == '-'
    _logger.info('SCons++ not checkout out yet, doing it now.')
    _exec_checked(['git', 'submodule', 'init'])
    _exec_checked(['git', 'submodule', 'update', 'external/scons-plus-plus'])

def update_spp() -> None:
    _logger.debug('Updating SCons++ submodule...')
    os.chdir(_root / 'external/scons-plus-plus')
    try:
        _exec_checked(['git', 'fetch', 'origin', 'master'])
        _exec_checked(['git', 'checkout', 'master'])
        output = _exec_get_output(['git', 'status', '--porcelain'])
        if output.strip() == '':
            return
    finally:
        os.chdir(_root)
    _logger.info('Changes in SCons++ detected, creating commit.')
    _exec_checked(['git', 'commit', '-m', 'Updated Scons++', 'external/scons-plus-plus'])

def _replace_in_file(file: Path, **replacements) -> None:
    _logger.debug('Patching file "%s"...', file)
    bakfile = file.with_suffix(f'{file.suffix}.bak')
    bakfile.unlink(missing_ok=True)
    file.rename(bakfile)

    with bakfile.open('r') as fin, file.open('w') as fout:
        for line in fin:
            def _repl(match: re.Match) -> str:
                return replacements.get(match.group(1), '<invalid variable>')
            fout.write(_variable_regex.sub(_repl, line))
    bakfile.unlink()

def setup_project() -> None:
    project_name = ''
    while project_name == '':
        print('Please enter a name for your project.')
        project_name = _prompt().strip()
    module_name = project_name
    print(f'Please enter a name for the first module. Leave empty to use the project name ("{module_name}").')
    new_name = _prompt().strip()
    if new_name != '':
        module_name = new_name
    
    module_folder_name = _escape_filename(project_name.lower())
    print(f'Please enter a folder name for the first module. Leave empty for "{module_folder_name}". Anything but [A-Za-z0-9_] will be replaced with underscores.')
    new_name = _prompt().strip()
    if new_name != '':
        module_folder_name = _escape_filename(new_name) # just enforce nice names

    module_exe_name = _escape_filename(module_name.lower())
    print(f'Please enter a file name for the module executable. Leave empty for "{module_exe_name}". Omit the file suffix. Anything but [A-Za-z0-9_] will be replaced with underscores.')
    new_name = _prompt().strip()
    if new_name != '':
        module_exe_name = _escape_filename(new_name)

    
    _replace_in_file(_root / 'SConstruct', PROJECT_NAME=project_name, MODULE_FOLDER_NAME=module_folder_name)
    _replace_in_file(_root / 'private/spp_template/SModule', MODULE_NAME=module_name, EXE_NAME=module_exe_name)
    
    template_folder = _root / 'private/spp_template'
    module_folder = _root / 'private' / module_folder_name
    _logger.debug(f'Moving {template_folder} to {module_folder}.')

    _logger.info('Creating a git commit for the setup.')
    _exec_checked(['git', 'commit', '-m', 'Project setup', 'SConstruct', 'private'])

if __name__ == '__main__':
    logging.basicConfig(level=logging.DEBUG, format='%(message)s')
    _root = Path(__file__).parent.parent
    os.chdir(_root)
    #try:
    verify_tools()
    download_spp()
    update_spp()
    setup_project()
    #except Exception as e:
    #    _logger.error('There was an error running the script: %s.', e)
    #    sys.exit(1)